Magnetic recorder



y 1947. w. P. LEAR umusnc nnconmm Filed lay 12, 1945 3 Sheets-Sheet 1 July 29, 1947.

W. P. LEAR MAGNETIC RECORDER Filed May 12, 1945 3 Sheets-Sheet 3 Aff- . mmvrm M104 I? 154/? @MZWK A ATTORNEY Patented July 29, 1947 MAGNETIC RECORDER William P. Lear, North Hollywood, Calif., assignor, by mesne assignments, to Lear, Incorporated, Grand Rapids, Mich., a corporation of Illinois Application May 12, 1945, Serial No. 593,378

This invention relates to a magazine type mag netic recording system and more particularly to a novel magazine for use therewith embodying mechanical elapsed talking time indicator and means for automatically interrupting recording when the talking time of the recording medium has been substantially fully utilized.

In magnetic recording systems of the type to which the present invention is directed, a maga" zine, containing the recording medium and mech" anism for traversing the same relative to a magnetic translating head, is provided with coupling elements detachably engageable with mating elements on a sound translating unit with which the magazine maybe interchangeably associated. Generally, the traversing means comprises a pair of spaced rotatable reels, which may be designated as storage and frewind reels. During recording or reproduction the linear magnetic recording medium is unwound from the rewind reel and wound on to the storage reel. It is desirable to provide suitable means for indicating to the operator the amount of talking time remaining on the recording medium wound on the rewind reel. Furthermore, in order to revent damage to the recording medium or other parts of the apparatus, the present invention provides automatic means for interrupting movement of the recording medium when the same has been substantially completely interchanged from the "rewindf reel to the storage reel.

It is therefore among the objects of this invention to provide a magazine type recording apparatus including a, sound translating unit, a magazine interchangeably operative therewith, and releasable means for automatically latching the magazine to the unitwhen the magazine is placed on the unit; to provide such a system including cooperating means on the magazine and unit'operable to interrupt traversing of a record ing medium with respect to a magnetic translating head when the recording time onthe medium has been substantially fully utilized; to provide such a system including means for indicating the amount of talking time remaining on the recording medium; and to provide a lightweight, in-

expensive, compact and efficient magnetic sound translating apparatusincluding a novel sound translating unit and a novel magazine interchangeably cooperative therewith.

These and other objects, advantages and novel features of the invention will be apparent from drawings. In the drawings:

13 Claims. (o1.179 100.2

Fig. l is a perspective View of bodying the present invention. 1

Fig. 2 is a plan view of a portion of a sound translating unit forming part of the'invention.

Fig. is a partially longitudinal sectional view through the sound translating unit and a magazine cooperable therewith.

Fig. 4-is a plan view of a magazine forming part of the invention.

Fig. 5 is an elevational view of the magazine taken substantially along the line 5-5 of Fig. 4; Fig. 6 is an elevation view, partly in section, on the line 6-6 Of'Fig. 4.

Fig.7 is a transverse sectional view on the line 11ofFig.4. Fig. 8 is a schematic wiring diagram illustratinga switch operating mechanism forming part of the invention.

According to'the present invention, magnetic sound translating apparatus is provided including a magnetic sound translating unit and a magazine interchangeably engaged therewith. The sound translating unit includes electronic sound translating means, driving mechanism operated by an apparatus emelectricmotor, a switch controlling the energization of the motor and having a projecting operating arm, mechanical coupling means connected to the driving mechanism and an electrical coupling means in electric circuit connection with the sound translating means. The unit likewise includes releasable latching elements adapted to automatically engage latching means on the magazine when thelatter is placed in operative relation with the unit. M

The magazine'includes a pair of reels for interchangeably receiving a magnetic recording medium and traversin the same with respect to a magnetic translating head, mechanical coupling elements for connecting the reels to the drivingm'echanism of the unit, spooling mechanism forlayer'winding the magnetic recording medium onto and off of the reels, indicating means for indicating the amount of talking time remaining on the recording medium, an operating member for the motor controllin switch, mechanism for operating the indicator and the switch operating member, and a mechanical coupling elementforconnecting the spooling mechanism and such operating mechanism to reduction gearing associated with the driving mechanism of the unit. The magazine isprovided with spaced latching means automatically cooperative with the latching elements of the unit for maintainingthe magazine in stablerelation with the unit when disposed thereupon. "Preferably,

the magazine includes a substantially flat rectangular base containing the aforementioned elements, and a rectangular cover detachably secured to the base and having a window for viewing the magazine indicating means.

Referring more particularly to Fig. l of the drawings, the recording apparatu is shown as comprising a magnetic translating unit I havin a magazine I interchangeably cooperable therewith. Translating unit I0 comprises a casing II to which is secured a control panel I2. The illustrated recording apparatus is adapted for use aboard aircraft, and for this purpose is made light in weight and compact. Control panel I2 is provided with a socket I3 to which a power supply may be connected, a socket I4 which may be connected to a remote control arrangement, a plug I6 adapted to receive a jack connected to the intercommunication system of the aircraft, another plug I! for receiving a jack connected to a microphone, a main control switch I8 with which is associated the indicating light 2I, a motor circuit control switch 22, a lamp 23 for indicating when the unit is recording and a fuse 24 mounted for ready accessibility in the event a replacement is needed. A knob is mounted on the control panel and associated with releasable latching means for automatically latching magazine I5 to unit 8. The operation of knob 20 will be described more in detail hereinafter.

Casing II includes a forward section 25 which may contain suitable electronic means for sound translating purposes. The casing likewise includes a rearward section 36 containing drive mechanism for magazine I5 and provided with an upper panel or surface 26 for receiving and supporting magazine I5. It will be noted that surface 26 is at a lower level than the top wall 21 of section 25, so that when magazine I5 i engaged with unit It, a uniform rectangular complete unit is provided.

Magazine I5 is detachably engageable with surface 25 of unit I5. The magazine includes a base and cover 3! detachably connectible thereto by screws 32. Cover 3i is provided with an aperture 33 which may contain a transparent member 34 having suitable indicia 36 cooperative with an indicating needle for indicating the amount of talking time remaining on the magnetic recording medium.

Magazine I5 is releasably latched to unit III. For this purpose, the magazine is provided with latching pin 51 adjacent each corner thereof which are engageable with latching elements 38, 38, and 45 pivoted on pins 42 mounted in translating unit II). Each of the latching elements comprises a bar having a rounded upper end 43 below which is a notch 44. Knob 20 is secured to or is integral with a bar 45 slidably mounted in a bearing 45 secured in forward section 25 of casing II. The rear end of bar 45 is pivoted to a pin 41 mounted in element 38. A link 48 connects pin 41 to a pin 50 in the lower end of element 39. A channel shaped member 5| rigidly interconnects elements 39 and 40. Elements 40 and 4I are pivotally interconnected by a link 52. A spring 53 extending between pivot pin 42 of element 38 and pin 58 secured to element 39 normally urges the elements to their inward or locking position. The elements are oscillatable in slots 54 adjacent each corner of surface 26, and each element has its notch 44 facing outwardly with respect to surface 26.

When magazine I5 is placed on surface 25, pins 31 engage the rounded upper ends 43 of the latchpins snap into notches 44 to automatically latch magazine I5 on unit I0. When it is desired to disengage the magazine from the unit, knob 20 is moved inwardly or depressed. This pivots the latching elements, as a unit, inwardly of surface 26 and permits magazine I5 to be lifted from unit I0.

Translating unit I6 and the parts of magazine I5 cooperating therewith are more clearly shown in Figs. 2 and 3. As shown, casing section 38 contains an electric motor 55 supported from mounting plate 26. A spiral gear 56 on the outer end of motor armature shaft 51 engages a spiral gear 53 on the lower end of a vertically extending shaft 55, Another spiral gear 6| secured in an intermediate position on shaft 56 drives a spiral gear 62 on a horizontally extending shaft 63. A spiral gear 54 on shaft 63 drives a spiral gear 65 secured to a shaft 66. The several spiral gears 52, 64 and 55 form a reduction gearing associated with motor 55 for a purpose to be described hereinafter.

A mechanical coupling element 61 is slidably secured to the upper end of shaft and is urged outwardly through an aperture 68 in mounting plate 26 by a spring 10. Coupling element 61 comprises a gear having axially extending teeth H with rounded outer edges, and is cooperable with a similar coupling element "I2 of magazine I5. A bracket I3 secured to mounting plate 26 supports a shaft I4 rotation of which is frictionally resisted by a spring 15 disposed between a nut I6 on shaft I4 and the lower side of bracket 13 The upper end of shaft 14 carries a coupling element I7, identical with coupling element 61, and urged outwardly through an aperture I8 in plate 26 by a spring 80. Coupling element 11 is cooperable with a mating coupling element 8I in magazine I5.

Th rearward end of shaft carries a spur gear 82 extending upwardly through a slot 83 in plate 26. Spur gear 83 is operated at a reduced rate with respect to coupling element 61 and TI due to the aforementioned reduction gearing. An angular bracket 85 secured near the rear edge of plate 26 (as viewed in Fig. 2) supports a switch 86 controlling the energization of motor 55. Switch 85 is preferably of the snap action type operated by a plunger 81. An operating arm 88 is pivotally mounted at 98 on bracket 85 and is formed with an ear or flange 9| adapted to engage plunger 87. The operation of arm 88 in controlling switch 86 is described more clearly hereinafter with particular referenc to Fig. 5. Pins 92, 93 and 94 are secured to mounting plate 25 to project thereabove to enter apertures in the base of magazine I5 to properly locate the magazine on surface 25.

Referring to Figs. 3 through '7, magazine I5 comprises a base I80, which is preferably a casting havin oppositely disposed side walls IUI IM and end walls I62, I02, Adjacent each end wall, each of the side walls is formed with a protuberance I63, with each protuberance having a slot I64 therein across which extend latching pins 31. Slots I64 receive the upper ends of latching elements 38, 39, 40 and 4| of unit II! when base I88 is engaged with plate 25, and, as described, pins 31 enter notches 44 of the latching elements to lock the magazine to the translating unit.

A pair of reels I35 and III! are rotatably mounted on base I68. For this purpose, base I00 is formed with vertical bushings I06, I61 containing bearings I08 rotatably supporting shafts III and H2. Studs H3, H4 detachably secure reels I05, M to shafts III, II2. Pins II5 extend through a flange II6 on each shaft and through the associated reel to secure the reels for rotation with the shafts. Coupling elements 12 and BI are secured to the lower ends of shafts I I I, II2 respectively, for coupling the reels to coupling elements 61 and 8| of unit I0, respectively. To maintain reels I05, IIO against rotation when magazine I5 is removed from unit I0, springs H1, H1 are secured to bushings I06, I01 and normally engage reels I05, IIO, As shown in Fig. 3, when magazine I5 is disposed on surface 26, pins 92, 94 enter through apertures in base I 00 and engage springs H1, H1 to spring the same inwardly and disengage each spring from its associated reel. The reels are thereby released for rotation under the control of the mechanism in unit I0.

Reel I 05 is the rewind reel and reel I I0 is the storage reel. In advance of a recording or reproduction operation, substantially all of a linear magnetic recording medium, such as a magnetic wire I20 is wound on rewind reel I05. During recording or reproduction, storage re l H0 is rotated by motor 55 through the associated gearing and coupling elements, to traverse wire I20 with respect to a magnetic translating head I25. During such operation, washer 15 exerts a frictional drag on shaft 14 connected to rewind reel I05 to maintain wire I20 taut between the reels.

Base I00 supports an electrical coupling element such as a socket I30 detachably engageable with a plug I35 mounted on plate 26 of unit I0. Socket I30 is electrically connected to magnetic translating head I25. Head I25, as seen more clearly in Figs. 4 and 6, is mounted on a plate I26 pivotally supported by bearings I 21, I28 for oscillation about an axis perpendicular to the axes of rotation of reels I05, IIO. Plate I26 is provided with flanges I3I, I32. An arm I33 is secured to flange I3I and has telescopically related therewith an arm I34 on the outer end of which is a casing I36. A spring I31 normally urges casing I36 outwardly away from plate I26 and toward reel I05. Casing I36 is provided with bearings I38 rotatably supporting grooved pulley I40. A similar casing I4I rotatably supporting a grooved pulley I42 in a like manner is secured to an outer end of an arm I43 fastened to flange I32 of plate I26.

Casings I36 and MI in cooperation with pulleys I40 and I42 guide wire I20 between head I25 and reels I05, I I0. The wire passes around each of the pulleys and toward the associated casings and is reversed in direction for winding on eithe of the reels, as shown more clearly in Fig. 4. Through oscillation of plate I26 about its axis, in a manner to be described more fully hereinafter, wire I20 is layer wound onto and oif of reels I05 and H0.

One of the side walls IOI of base H0 is offset inwardly as at I45 to provide a recess I46 closed by removable plate I41. Wall I45 and plate I41 rotatably support a shaft I48, on the inner end of which is secured a reentrant cam I50. Next to cam I50, a spur gear I5I is secured to shaft I48 and is adapted to engage spur gear 82 of unit 83. For this purpose, base I00 is provided with a slot I52 (Fig. 6) which is aligned with a slot 83 in plate 26. Cam I50 is engaged by a cam follower I53 extending from plate I26 and urged into continuous engagement with cam I50 by a leaf spring I54 secured to base I00. Rotation of cam I50, through the interengagement of gears 82 and I5I, oscillates plate I 26 to layer wind wire I20 onto and off of reels I05, IIO.

A pair of pillow blocks I56, I56 (Figs. 4 and 5) secured to the outer surface of wall I45, rotatably support a threaded shaft I55 having on one end a bevel gear I51 meshing with a. bevel gear I58 on shaft I48. Rotation of gear I5I will thus effect rotation of shaft I55. A travelling nut I60 is threadedly engaged with shaft I55 and held against rotation thereon by sliding engagement with wall I45 (Fig. 7). Nut I60 carries the needle 35 cooperable with the indicia on transparent plate 34 visible through aperture 33 in cover 3| of magazine I5.

A vertical bar I6I is provided with a pair of slots I62, I62 through which extend studs I63, I63 slidably supporting the bar with relation to wall I45. Bar I6I is provided with vertical flanges I64, I65 which project into the path of nut I60. A stud I66 is adjustably mounted in flange I65 for predetermining the point of effective engagement of nut I60 with bar I6I, Bar I6I is also provided with a horizontal ear or flange I61 provided with a slot I 68 aligned with an aperture I10 in base I00, which is in turn aligned with an aperture I1I in plate 26 in unit I0, through which projects the upper end of operating arm 88 for switch 86.

The operation of the indicating and switch operating mechanism is as follows. During energization of motor 55, shaft 66 is rotated by the gear reduction unit associated with the motor. This correspondingly rotates spur gear 82 in correspondence with therotation of coupling elements 61 and 11 of unit I0. Thus, spur gear I5I of magazine I5 is rotated in correspondence with the rotation of reels I05 and H0 of the magazine. Such rotation of spur gear I5I, through cam I50 and cam follower I53, effects oscillation of plate I26 about its pivot to layer wind wire I20 onto and off of the reels. At the same time, through bevel gears I51, I58, threaded shaft I55 is rotated to cause nut I60 to travel therealong. Movement of nut I60 moves indicating needle 35 with respect to indicia 36 on transparent member 34, so that the operator is apprised of the relative amounts of wire I20 on each of the reels.

The direction of the threads on shaft I55 is such that nut I60 travels to the right, as viewed in Fig. 5 (or to the left as viewed in Fig. 4) during a recording or reproducing operation. Accordingly, when substantially all of the talking time on wire I20 has been utilized, which means that the wire is substantially completely unwound from rewind reel I05 and wound on to storage reel IIO, nut I60 abuts tappet I66 tomove bar I6I to the right (Fig. 5) and thus to swing arm 88 in .a counter-clockwise direction (Fig. 3) to depress button 81 of switch 86 to open the switch and break the energizing circuit for motor 55. This interrupts travel of recording medium I20. If desired, a second switch could be mounted on bracket 85 for operation of swinging movement of arm 68 in the opposite direction during a rewinding operation to interrupt the energization of motor 55 when the wire has been substantially all rewound on reel I05.

Fig. 8 diagrammatically illustrates the operation of the magazine elements in controlling the energization of motor 55. In this figure, motor 55 is illustrated as comprising an armature I10 and a series field winding I1I. However, motor 55 may be a shunt or compound wound motor, if de-' sired. The energization of motor 55 is controlled from a suitable source of power I12, indicated for reference purposes as a battery, through main switch 22 and snap action switch 86. Switch 86 is provided with a switch blade I13 having an operating button 8'! engaged by the flange 9i on arm 83. As travelling nut I50 moves to the left in Fig. 8, it engages tappet 166 to slide bar lBl to the left pivoting arm 88 counter-clockwise to depress button 87 disengaging switch arm I13 from contact [14 to break the energizing circuit for motor 55.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles thereof, it will be understood that the invention may be otherwise embodied, without departing from such principles.

What is claimed is:

l. A magazine adapted for interchangeable latching engagement with a magnetic sound translating unit, said magazine comprising a base formed with a bottom wall and rectangularly disposed side and end walls, and containing a linear magnetic I'eCOrding medium and means for traversing said medium with respect to a magnetic translating head; each side wall being formed with a protuberance adjacent each end wall, said protuberances being formed with slots adapted to receive latching bars on the unit; a pin extending across each slot and automatically engageable with the unit latching bars when the magazine is engaged with the unit to retain the magazine and unit in stable cooperative relationship; and a cover detachably secured to said base.

2. A magnetic sound translating unit adapted for interchangeable cooperation with a magazine containing a linear magnetic recording medium and means for traversing the medium with respect to a magnetic translating head, said unit comprising a casing formed with a surface adapted to receive and support the magazine; spaced pairs of latching elements pivotally mounted in said casing and projecting above said surface for automatic engagement with latching means on the magazine when the latter is placed on said surface to retain the magazine and unit in stable cooperative relationship; and means for operating said elements to disengage the magazine latching means to provide for disengagement of the magazine from said unit.

3. A magnetic sound translating unit adapted for interchangeable cooperation with a magazine containing a linear magnetic recording medium and means for traversing the medium with respect to a magnetic translating head, said unit comprising a casing formed with a substantially rectangular fiat surface adapted to receive and support the magazine; latching elements pivotally mounted in said casing and projecting above said surface adjacent each corner thereof for automatic engagement with latching means on the magazine when the latter is placed on said surface to retain the magazine and unit in stable cooperative relationship; means interconnecting said elements for operation as a unit; and manually operable means connected to said elements and operable to disengage the same from the magazine latching means to provide for disengagement of the magazine from said unit.

4. A magnetic sound translating unit adapted for interchangeable electrical and mechanical cooperation with a magazine containing a linear magnetic recording medium and means for traversing the medium with respect to a magnetic translating head, said unit comprising a casing having a front control panel, a forward section containing sound translating apparatus, and a rearward section containing driving mechanism and formed with a substantially rectangular flat surface adapted to receive and support the magazine; a first pair of latching bars pivotally mounted in said rearward section adjacent the rear corners of said surface and projecting thereabove; means rigidly interconnecting said first pair of bars; a second pair of latching bars pivotally mounted in said rearward section adjacent the forward corners of said surface and projecting thereabove; a link pivotally connecting each bar of said second pair to a bar of said first pair; said bars automatically engaging latching means on the magazine when the latter is placed on said surface; spring means maintaining said bars in the latching position; and a release bar slidably mounted in said forward section, projecting beyond said panel and pivotally connected to a bar of said second pair, depression of said release bar pivoting said latching bars to disengage the magazine latching means.

5. A magazine adapted for interchangeable cooperation with a magnetic sound translating unit containing sound translating means and driving mechanism, said magazine comprising reels for traversing a linear magnetic recording medium with respect to a magnetic translating head; coupling elements associated with said reels for mechanically coupling the same to the unit driving mechanism; indicating means for indicating the progress of the medium relative to the translating head; spooling mechanism for layer winding the medium onto and off of said reels; and a coupling element commonly associated with both said indicating means and said spooling mechanism for disengageably mechanically coupling the same to the unit driving mechanism.

6. A magazine adapted for interchangeable cooperation with a magnetic sound translating unit containing sound translating means, driving mechanism, an electric motor for the mechanism, a switch controlling the motor, and an operator for the switch, said magazine comprising means for traversing a linear magnetic recording medium with respect to a magnetic translating head; coupling elements associated with said traversing means for mechanically coupling the same to the unit driving mechanism; a member adapted to engage the switch operator of the unit to operate the switch to deenergize the motor; mechanism operable in synchronism with said traversing means to operate said member; and a disengageable coupling element associated with said mechanism for independently mechanically coupling the same to the unit driving mechanism.

7. A magazine adapted for interchangeable cooperation with a magnetic sound translating unit containing sound translating means, driving mechanism, an electric motor for the mechanism, a switch controlling the motor, and an operator for the switch, said magazine comprising reels for traversing a linear magnetic recording medium with respect to a magnetic translating head; coupling elements associated with said reels for mechanically coupling the same to the unit driving mechanism; spooling mechanism for layer winding the medium onto and oif of said reels; a member adapted to engage the switch operator of the unit to operate the switch to deenergize the motor; operating mechanism for said memher; and a coupling element commonly connected to both of said spooling and operating mecha nisms for disengageably mechanically coupling the same to the unit driving mechanism.

8. Amagazine adapted for interchangeable cooperation with a magnetic sound translating unit containing sound translating means and driving mechanism including reduction gearing, said magazine comprising reels for traversing a linear magnetic recording medium with respect to a magnetic translating head; coupling elements associated with said reels for mechanically coupling the same to the unit driving mechanism; indicating means for indicating the progress of the medium relative to the translating head; spooling mechanism for layer winding the medium onto and off of said reels; and a coupling element commonly associated with both said indicating means and said spooling mechanism for disengageably mechanically coupling the same to the unit reduction gearing for operation at a reduced rate relative to said reels.

9. A magazine adapted for interchangeable cooperation with a magnetic sound translating unit containing sound translating means, driving mechanism, including reduction gearing, an electric motor for the mechanism, a switch controlling the motor, and an operator for the switch, said magazine comprising reels for traversing a linear magnetic recording medium with respect to a magnetic translating head; coupling elements associated with said reels for mechanically coupling the same to the unit driving mechanism; spooling mechanism for layer winding the medium onto and off of said reels; a member adapted to engage the switch operator of the unit to operate the switch to deenergize the motor; operating mechanism for said member; and a coupling element commonly connected to both of said spooling and operating mechanisms for disengageably mechanically coupling the same to the unit reduction gearing for operation at a reduced rate relative to said reels.

10. A magazine adapted for interchangeable cooperation with a magnetic sound translating unit containing sound translating means, driving mechanism, an electric motor for the mechanism, a switch controlling the motor, and an operator for the switch, said magazine comprising means for traversing a linear magnetic recording medium with respect to a magnetic translating head; coupling elements associated with said traversing means for mechanically coupling the same to the unit driving mechanism; indicating means for indicating the progress of the medium relative to the translating head; a member adapted to engage the switch operator of the unit to operate the switch to deenergize the motor; operating mechanism commonly connected to both said member and said indicating means; and a. disengageable coupling element associated with said operating mechanism for independently mechanically coupling the same to the unit driving mechanism.

11. A magazine adapted for interchangeable cooperation with a magnetic sound translating unit containing sound translating means, driving mechanism, an electric motor for the mechanism, a switch controlling the motor, and an operator for the switch, said magazine comprising reels for traversing a linear magnetic recording medium with respect to a magnetic translating head; coupling elements associated with said reels for mechanically coupling the same to the unit driving mechanism; spooling mechanism for layer Winding the medium onto and off of said reels;

. 10 indicating means for indicating the progress of the medium relative to the translating head; a member adapted to engage the switch operator of the unit to operate the switch to deenergize the motor; operating mechanism commonly connected to both said member and said indicating means; and a coupling element commonly connected to both of said spooling and operating mechanisms for disengageably mechanically coupling the same to the unit driving mechanism.

12. A magazine adapted for interchangeable cooperation with a magnetic sound translating unit containing sound translating means, driving mechanism, including reduction gearing, an electric motor for the mechanism, a switch controlling the motor, and an operator for the switch, said magazine comprising reels for traversing a linear magnetic recording medium with respect to a magnetic translating head; coupling elements associated with said reels for mechanically coupling the same to the unit driving mechanism; spooling mechanism for layer Winding the medium onto and off of said reels; indicating means for indicating the progress of the medium relative to the translating head; a member adapted to engage the switch operator of the unit to operate the switch to deenergize the motor; operating mechanism commonly connected to both said member and said indicating means; and a coupling element commonly connected to both of said spooling and operating mechanisms for disengageably mechanically coupling the same to the unit reduction gearing for operation at a reduced rate relative to said reels.

13. A magazine adapted for interchangeable cooperation with a magnetic sound translating unit containing sound translating means, driving mechanism, including reduction gearing, an electric motor for the mechanism, a switch controlling the motor, and a pivotally mounted projecting operating arm for the switch, said magazine comprising a, pair of reels mounted adjacent either end of said magazine for interchangeably receiving a linear magnetic recording medium; coupling elements associated with said reels for mechanically coupling the same to the unit driving mechanism; a member pivotally mounted between said reels for oscillation about an axis perpendicular to the axes of said reels; a magnetic translating head mounted on said member; elements projecting from said member toward each of said reels for guiding said medium between said head and said reels; a reentrant cam rotatably mounted in said magazine; a cam follower secured to said member and engaging said cam to oscillate said member to layer wind the recording medium onto and off of said reels; a, threaded shaft rotatably mounted in said casing; a travelling nut operatively associated with said shaft; a bar slidably mounted in said casing adjacent said shaft, said bar having an aperture adapted to receive the projecting end of the switch operating arm and arms projecting into the path of said nut; gearing connecting said cam and said shaft; 3, coupling element secured to said cam for mechanically coupling said cam and said shaft to the unit reduction gearing for operation at a reduced rate relative to said reels; and an indicator movable with said nut for indicating the relative amounts of recording medium on each of said reels; said nut sliding said bar to swing the switch operating arm to open the switch to deenergize said motor when sub- 11 stantially all of said recording medium has been transferred from one of said reels to the other.

WILLIAM P. LEAR.

REFERENCES CITED The following references are of record in the file of this patent:

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